Method of making ore agglomerates

ABSTRACT

A method is provided for producing lump metal ores by admixing the finely divided ore with an alkaline earth oxide or hydroxide and a carbonaceous material, forming the mixture into lumps and reacting it with carbon dioxide in the presence of moisture to form alkaline earth carbonates in situ in the lumps.

United States Patent [72] inventor Louis George lrnperato, Jr.

' Tenafly,N.J.

[21] Appl. No. 806,672

[22] Filed Mar. 12, 1969 V Continuation-impart of Ser. No. 672,003, Oct.2, 1967, Continuation-impart Ser. No. 374,191, June 10, 1964, Pat. No.3,382,063.

[45] Patented Nov. 2, 1971 [73] Assignee Blocked Iron Corporation Theportion of the term of the patent subsequent to May 7, 1985, has beendlsclallned.

[54] METHOD OF MAKING ORE AGGLOMERATES 501 Field of Search .111. 75/3Primary Examiner-Allen 8. Curtis Auomey- Buell, Blenko & ZiesenheimABSTRACT: A method is provided for producing lump metal ores by admixingthe finely divided ore with an alkaline earth oxide or hydroxide and acarbonaceous material, forming the mixture into lumps and reacting itwith carbon dioxide in the presence of moisture to form alkaline earthcarbonates in situ in the lumps.

METHOD OF MAKING OlRlE AGGLOMERATES This application is acontinuation-in-part of my copending application Ser. No. 672,003, filedOct. 2, 1967, which is a continuation-in-part of my application Ser. No.374,191, filed types of pellets heretofore made and is a very distinctadvantage to be gained by the practice of this invention. l have foundthat this can be accomplished within the range of coal concentration setout hereinabove, although I prefer to use June 10, 1964 now U.S. Pat.No. 3,382,063. This invention re- 5 about l percent minus l00-mesh coalwhen forming specular lates to ore agglomerates and methods of makingthe same and hematite balls or pellets. particularly to high strengthand at least partially self-reducing The amount of alkaline earth oxideor hydroxide, e.g. lime, iron ore agglomerates and methods of makingsuch agpreferably lies in the range from about to 20 percent byglomerates. weight of the admixture.

The need for a satisfactory method of agglomerating iron Iprefer to adda small amount (up to about 2 per ent) )of and other ores, particularlyoxide ores. has long been recogsolubilizing agent for calcium andmagnesium, as disclosed in nized. As the high purity, lumpy ores of theMesabi and other y p e a .9 u s a uga n a ning ranges have beenexhausted it has been necessary to turn to material. -gblaCkStfaPmolasses. g fructose. dextrose, ore concentrates recovered from lesspure ore deposits and to sy p the llkfi og he h a Small m n of a min ralfine ores not heretofore considered suitable for steel making. 5 acidSalt of an alkali lin earth me l h as C ium in order to make these oressuitable for handling and use in Chloride in all amount 1858 1 about 10percent 1 ay also add steepmelting furnaces i h b necessary toagglomerate a small amount of an alkali metal oxide or hydroxide such asthese ores into larger pieces. This has conventionally been Sodlumhydroxldet P y the range of about done by pelletizing or briquetting thefine ores and sintering or about p f I fusing the pellets or briquettesto form the solidified ag- The Practlce of my Invention Produces aresumng Pmducl glomerates. Sintering requires extremely hightemperatures Whlch 1135 high strength after b81118 sublecled to elevatedand large capital outlays in temperature-resistant equipment. Pefatures.'g- 1900' and WhlCh Shows a gh p r- 1 have invented an ore agglome ate dh d f ki centage of reduced iron after such heating indicating that thesuch agglomerates which is much less expensive than these t'noclll iSself-reducing. Both of these properties are highly sintered agglomeratesand is at least partially self-reducing. gh after n fi -l t0 hl i in thepreferred practice of my invention 1 admix ore fines The practice of myinvention can perhaps best be explained with an oxide or hydroxide of analkaline earth metal, a finely y r ren to he f llo ing examples whichhow the sigdivided carbonaceous material of the group consisting of coall'llficances 0f the p a ice my in n i n- (both bituminous andanthracite), coke, graphite, charcoal, EXAMPLE] coke breeze andoptionally with a small amount of a mineral Pellets were made byadmixing lime hydrated and specular acid salt of an alkali metal, or analkaline earth metal and/or a hematite or taconite concentrates withcoal. The resulting pelsmall amount of an alkali hydroxide together withsufficient lets were subjected to carbon dioxide sufficient to formwater to permit the formation of agglomerates such as pellets,recrystallized limestone in situ. The carbonated pellets were briquettesor blocks. These agglomerates are then subjected to then divided intotwo parts, one heated to l.600 F., and the an atmosphere of carbondioxide for a time sufficient to conother to 1,700 F. in an atmospherecontaining carbon monox- Vert a major portion of the alkaline earthoxide or hydroxide ide such as would be encountered in a blast furnaceor like to carbonate. iron-handling furnace. The pellets were removedand analyzed 1 have found that the moisture level for most effective forreduced iron. The results are tabulated in Tablel. operatron of myprocess ls below 10 percent by weight of'the 40 TABLE I CARBONATE BONDEDPELLET SUMMARY total admlxture and preferably in the neighborhood of 5per- Cent or less. Percent reduction Preferably the carbonaceousmaterial used in my process is 1,600 F. 1,700 F. finely dividedbituminous coal and I shall hereafter dlscuss the Taconite concentrate:invention in terms of iron ores the bituminous coal. I prefer Gperccntlime hydrate"... 38.7 44.8 the size range of 4-mesh and under for thecoal used and good %3i volume 49 1 81 5 results have been attained atboth ends of the range as well as Specular hematite Canasta-m; D H withmixtures of varying particle size coal. 1 have found that gg ig 39's45.6 amounts between about 1 percent and 15 percent of coal by23%regroulnddsplicultgrl1?ln'lr;1titel(?i325 M+ {28.3 74.1 weight aremost satisfactory for my purposes, although larger 50 s g fs a g g z g fi fi fi amounts to 25 percent have been satisfactorily used inpractlchydrate+l0% high volatile coal 49.1 37. 1

- ing my process. I have found that the use of minus l00-mesh coal makesit possible to ball or pelletize conventional as EXAMPLE llreceived"specular hematite concentrate without the addition Anadditional series of pellets were made as in Example I ofregroundhematite or without the addition ofany other fine and after removal fromthe heating furnace at l,600 and ore. Prior to my invention, it had beenimpossible to form balls l,700 F., respectively, were screened todetermine the or pelletize specular hematite by usual balling orpelletizing amount above 4-mesh and the amount below 20-mesh. Theymethods without regrinding or adding another fine ore. This were thenjarred for 15 minutes in a container and again has been one of the veryreal problems in the heat-indurated screened. The test results appear inTable ll.

T ABLE II Screen test from furnace at Screen test after jarring at-1,600" F. 1,700 F. 1,600 F. 1,700 F. +4M 20M +4M 20M +4M 20M +4M -20MTaconite:

6% lime hydrate 96. 7 1. 67 96.9 1. 48 43.7 51. 8 9% lime hydra 99.9 0.199.87 0.13 77.82 21:96 78.28 21.62 12% lime hydrate 99. 6 0.3 99. 5 0.283. 9 15. 9 82.8 16. 8 9% lime hydrate+10% high volatile coal 8 M) 99. 20. 38 97.6 0. 13 80. 64 17.30 80.09 15.0 9% lime hydrated-8% highvolatile coal (-8 M) and 2% low Volatile coal (-8 98. 62 0.61 99.47 0.2381.00 16. 98 84.17 14. 24 9% lime hydrate+8% high volatile coal (-8+150M) and 2% low volatile coal (-8+150 M) 96.69 0. 56 98. 57 0.42 81.7714.23 78.77 17. 37 Specular hematite:

25% reground (-325 M)+5% lime hydrate+ 15% high Volatile coal (-100 M)99.60 0. 35 96.80 2. 54 76.77 20.17 57.12 36. 61 Venezuelan ore:

Plus 1.76 lime hydrate 97. 59 0. 87 60. 43 32. 41 6% lime hydrnte+15%high volatile coal 3,617,254 3 4 EXAMPLE 111 TABLE v1 A series of testswere made on pellets produced by mixing together lime hydrate, specularhematite ore in both the as received and the reground" forms as inExample I but sub- Green B ll Physical Characteristics stituting variousother types of carbonaceous material for coal 5 Im an Resistance linesand omitting the molasses and chloride. The resulting 5 pellets weresubjected to an atmosphere of carbon dioxide as Number of Drops from inExample I to form recrystallized limestone in situ. TheseHeightorliv'onm A 1 Pl R a hardened pellets were tested as were thepellets in Example ll. l

to The results of the tests appear in T ble III Pellet Moisture Fracturean Individually "1 By Weight. Dry Dropped Ball ball Sample Number BasisAverage) 1 12.10 11 TABLE IIL-ROOM TEMPERATURE STRENGTH DATA l5 :1,Pellet composition:

Specular hematite as received, percent, 17 Specular hematite reground,percent, 70 I Lime hydrate, percent, 9 The pellets were d1'1ed prior toexposure and treatment w1th carbonacems materials must percent 4 20carbon dioxide to the levels of moisture set out in Table Vll.

Tumble test, Compression 0/0+% 280 TABLE V" carbonaceous materials, typetest, lbs. rev.

Coke breeze 161 96 ?;g$ Before exposure and treatment with carbondioxide charcoal: 173 96 gas. the green wet pellets were dried to amoisture N content indicated below:

Sample Number Dried Pellet Moisture, i

Dry Basil lRun 1 4.72 EXAMPLE 1v Run 1 11 Rub 1 4.17 Pellets made forExample ill were then treated in the heated I jg;

, un furnace as in Examples l and ii. The test results appear in Run 2 6Table IV.

TABLE IV Pellet composition:

Specular hematite as received, percent, 17 Specular hematite reground,percent, 70

Lime hydrate, percent 9 carbonaceous materials, various, percent, 4

Screen test from furnace at- Screen test after jarring at- 1600 F. 1,700 F. 1, 600 F. 1, 700 F. carbonaceous materials, types +4 M -20 M +4 M-20 M +4 M -20 M +4 M -20 M Coke breeze 99. G Anthracite 99. 8 Graphite-99. 7 CharcoaL 99. 6 Heat-lndurated taconite pellet 91.67

EXAMPLE V TABLE ViiI.-CARBONATED PELLE'I STRENGTH I CHARACTERISTICSCopper concentrates were m1xed with dolom1t1c fines and C h, ml coalfines to form three different compositions. These were i f 5 pelletizedand tested. The compositions are set out in Table V. ball e) ball e)Abrasion Sample Number %z"+ resistance TABLE V I Run 1- 67 104 52. 4IRun 2- 80 91 66.2 11 Run 1- 90 117 81.0 lgIIRRuiJ 2i 77 96 7g. 0 un "U92 7 0 Test Sample, ldent1ficat1on and composltlon 111 n 2 10 61, 40. 6sample Numb" Composition 1 Measured as the average total load in poundsrequired to fracture an individual pellet; with the size consistindicated.

2 Measured as the percent by Weight 01 material remaining in u fivepound test sample of pellets which had previously been rotated in an I5: 2:2 f zzfg ASTM coke tumbling drum for 200 revolutions. ll 93% byweight Copper Concentrate P"" A sample of pellets were heated innitrogen from room temm 5:52;:ggsgzr perature to l,600 F. inapproximately 60 minutes and the 4% COM sample remalned 1n the n1trogenatmosphere at l,600 F. for 5% Dolomitlc Hydra" an additional hour. Thespecimens were cooled in nitrogen to room temperature, removed from thefurnace, and tested as follows: The green ball physical characteristicsof these pellets of Crushing Strength: Ten pellets were removed from thesamcopperconcentratesare setoutin Table VI. ple and the average loadrequired to fracture an individual pellet was determined.

Abrasion Test: The remainder of the sample was placed on a 4-mesh sievescreen which was then put into a Ro-Tap shaker apparatus and jarred for15 minutes. The percent by weight of the material remaining on the4-mesh screen 5 after jarring was determined.

Thetesfi-esults are set out in ism e IX While I have described certainpreferred practices and products according to my invention, it will beunderstood that this invention may be otherwise embodied within thescope of the following claims. 1. The method of producing a highstrength, self-reducing lump ore from finely divided metalcontainingmaterials comprising the steps of admixing the finely divided metal orecontaining material with at least one of the group consisting of theoxides and hydroxides of alkaline earth metals and with a carbonaceousmaterial from the group consisting of coal, coke, graphite, coke breezeand charcoal, forming the mixture into lumps and reacting the lumps withcarbon dioxide in the presence of moisture to form alkaline earthcarbonates in situ in the lumps.

2. The method as claimed in claim 1 wherein the carbonaceous material iscoal having a fineness of 4-mesh and under.

3. The method as claimed in claim 1 wherein the metal ore is copperconcentrates.

TABLE [X Sample Crushing Strength, +4M After 10 Number in pounds Jarringl RUN 2 s 31.7 ll Run l 101 51.9 m Run 1 27 48.5

it will be evident from the foregoing tables and examples that a highstrength pellet capable of a high level of self-reduction can beachieved by the practice of my invention.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,617,254 D te November 2. 1971 Invent0r(s) L It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Column 3, Example V, Table V, Sample Number II, "22% percent Coal Fines,should read 2% Coal Fines Signed and sealed this 24th day of October1972.

(SEAL) Attest:

ROBERT GOTTSCHALK EDWARD M.FLETCHER,JR.

Commissioner of Patents Attesting Officer USCOMM-DC 60376-P69 RM PO-IOSO(10-69) h u 5 GOVERNMENT Pmmm; OFFICE was o:ss-:134

2. The method as claimed in claim 1 wherein the carbonaceous material iscoal having a fineness of 4-mesh and under.
 3. The method as claimed inclaim 1 wherein the metal ore is copper concentrates.